Recent advances in sound transmission technology have lead to the development of new headphones or headsets for use in telecommunications and entertainment applications in both external environments, such as military field operations, and internal environments, such as home use for listening to music and/or radio and television broadcasts. Headsets normally include one or a pair of earcups which fit over the outer ear and which are held in place by hand or by means of a head band which extends over the top of or behind the wearer's head. In addition to sound quality, wearer comfort is of primary concern to the user, particularly if the headphones are to be worn over an extended time period.
Headphone designs intended to improve both headphone sound quality and wearer comfort are disclosed in U.S. Pat. No. 4,455,675 issued to Bose et al, Jun. 19, 1984 and in U.S. Pat. No. 4,644,581 issued to Sapiejewski, Feb. 17, 1987. The headphones which are the subject of those disclosures include headphone cavities and electroacoustical transducers such as pressure-sensitive microphones positioned within the cavities respectively for providing signals which correspond to the sum of external noise and the sound produced by the headphone driver in each cavity. These designs include internal circuitry which reduces noise and distortion and improves the quality of the sound output to the ear and a cushion in contact with the ear to enhance wearer comfort.
More recently, U.S. Pat. No. 4,922,542 issued to Sapiejewski, May 1, 1990 discloses a headphone in which each earcup includes a baffle which supports a driver for converting an electrical input signal into an acoustical output signal to the ear. The baffle defines an inner and an outer cavity, the outer cavity being positioned adjacent the wearers ear and encompassed by a cushion surrounding the outer ear and sealing the outer cavity from the surrounding external environment. Similarly, U.S. Pat. No. 5,181,252 issued to Sapiejewski et al., Jan. 19, 1993 discloses a headphone having a high compliance driver mounted on a baffle which divides the headphone earcup into two chambers, each chamber having a preselected compliance which is individually matched to the compliances of the other chamber and the driver respectively to maximize the quality of the acoustical output. U.S. Pat. No. 7,412,070 issued to Kleinschmidt at al., Aug. 12, 2008 discloses a headphone having a pair of earcups, each earcup having a loudspeaker driver located off-center in an internal cavity. However, the designs of the '542, the '252 and the '070 disclosures do not adequately address the problems associated with acoustic interference and cancellation phenomenon associated with multi-chamber headphone designs, nor do they address the problem of volume balance control.
The headphone design of the present invention overcomes these and other problems by providing a new and novel headphone design which eliminates the internal acoustical compliance-related issues associated with a multi-chamber headphone earcup construction and a volume balance control feature which will permit the wearer to selectively psychoacoustically calibrate, adjust and balance the sound volume in each earcup. More specifically, the present invention provides a single chamber earcup having the microphone and driver mounted inside the earcup in such a manner that the baffle is eliminated, thereby permitting free flow of air throughout the entire cavity formed by the back of the earcup and the side of the wearers head. Means are provided to support the driver and the microphone at a predetermined location within the earcup that is sufficiently removed from the wearer's outer ear to prevent damage to the microphone which could result from contact with the pinna and during the process of putting on and/or removing the headphones, yet which is sufficiently close to the ear canal to maximize the quality of the sound delivered to the eardrum. An improved battery cover or cap is also provided.